I sent a post to -general with a much more detailed brain dump of my current
understanding on this topic. The main point I'm addressing here is how to
recover from this problem.
Since a symptom of the problem is that pg_dump/restore can fail saying that
(in some instances) the only viable restore mechanism be pg_dump/restore
means that someone so afflicted is going to lose data since their last good
dump - if they still have one.
However, if the true data table does not actually contain any duplicate data
then such a dump/restore cycle (or I would think REINDEX - or DROP/CREATE
INDEX chain) should resolve the problem. Thus if there is duplicate data
the user needs-to/can identify and remove the offending records so that
subsequent actions do not fail with a duplicate key error.
If this is true then providing a query (or queries) that can provide the
problem records and delete them from the table - along with any staging up
that is necessary (like first dropping affected indexes if applicable) -
would be good a nice addition.
David J.
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